The challenge of converting heat energy to electricity has been addressed by numerous approaches including thermoelectric, thermophotovoltaic, thermionics, Brayton, Rankine, and Stirling based devices. The disadvantage with these devices is that, although the devices have no moving parts, they have a low efficiency. Further, the devices that have higher efficiency have moving parts, which in turn are more complex to design and build.
Others have attempted to combine thermo-acoustics with piezoelectrics to create a high efficiency device that has no moving parts. These attempts, however, still suffer from significant losses due to convective steady flows being induced in the toroidal feedback designs needed to achieve a resonant high amplitude traveling acoustic wave.